The present invention relates generally to high-performance, self-adjusting, protective coatings and methods of manufacture. These coatings are capable of conforming to the geometrical and mechanical configurations of substrates to which they are applied. Accordingly, the invention also relates to metallic, ceramic, and polymeric substrates having novel friction, wear, and corrosion resistant metallic coatings firmly bonded thereto. The coatings, which have low porosity, and therefore, are smooth and substantially continuous with minimal defects, are characterized by enhanced wear and heat resistant properties, have a broad range of useful applications, e.g., in motor vehicle components, machinery, and so on.
Most brakes are of a frictional type in which a fixed surface is brought into contact with a moving part that is to be slowed or stopped. The limitations on the applications of brakes are similar to those of clutches except that the service conditions are more severe because the entire energy is absorbed by slippage which is converted to heat that must be dissipated. One important aspect is the rate at which energy is absorbed and heat dissipated. With frictional brakes, if the temperature of the brake becomes too high, the result is a lowering of the friction force, called fading. Modem brake rotors/drums and clutches, for example, require specific properties to be able to withstand in some instances, extreme operating conditions often associated with high performance motor vehicles, including racing cars.
Intermetallic compounds are known in the art to provide some of these desired properties. Intermetallic compounds are generated by chemical reactions between two or more metals. In general they have ceramic-like properties, such as high strength (especially at high temperatures) and excellent erosive and corrosive resistance. They have some properties superior to ceramics, such as better adhesion and ductility. However, after their application onto a substrate, intermetallic compounds are difficult to form or polish due to their brittle nature at room temperature. In contrast, chrome and nickel are easy to form or polish, but they corrode, erode, and oxidize easily.
One type of intermetallic coating is disclosed by U.S. Pat. No. 5,820,940 (Gorynin et al). This patent teaches an adhesive coating prepared from thermally reactive binary and multicomponent powders. It is a diffusion type intermetallic coating wherein thermally reactive metal powders containing aluminum are introduced into a plasma torch. An exothermic reaction within the thermally reactive powders is initiated in the plasma torch, which is completed after impingement of the exotherm onto the substrate. According to the United States Patent, the heat generated by the exothermic reaction promotes diffusion of the intermetallic compound into the substrate for improved bonding.
While the methods of Gorynin et al. allow for excess unreacted aluminum remaining dispersed throughout the layer for imparting ductility and flexibility, means for controlling final surface properties and minimizing surface defects, such as high porosity, lack of smoothness, or for preventing cracks from developing during the cool down stage, are neither taught nor suggested. Surface characteristics, including shape, surface smoothness/roughness, porosity and crack development, and other microstructural defects are not readily prevented by mechanically working (shaping or polishing) after such coatings are substantially fully reacted.
Accordingly, there is a longfelt need for a economical method to form an intermetallic coating on a substrate that allows working of the material to form it into the desired shape for removal of flaws.
The present invention broadly comprises a method for forming a metallic coating on a substrate comprising an intermetallic compound, and the coatings made by this method. The method broadly comprises forming an alloyed agglomerate from a precursor comprising at least two metals suitable for forming an intermetallic compound and depositing a coating of the partially converted agglomerate onto a roughened surface of a substrate.
A general object of the present invention is to provide a method for forming a metallic coating on a substrate comprising an intermetallic compound.
It is another object of the present invention to provide an economical method for forming a coating by a method that allows the working of the material into the desired shape, and the removal of flaws.
It is yet another object of the present invention to provide an economical method for forming particulates comprising an intermetallic compound.
It is yet another object of the present invention to provide an economical method for bonding together two surfaces using a metallic layer comprising an intermetallic compound.
This and other objects, features and advantages of the present invention will become readily apparent to those having ordinary skill in the art upon a reading of the following detailed description of the invention in view of the claims.